The present invention relates to a ring network, a communication device, and an operational management method used for the ring network and communication device. In particular, the invention relates to a communication device having an RPR (Resilient Packet Ring) function.
Regarding the above RPR function, a network protocol called “RPR” marked by effective utilization of a transmission capacity, a high-speed hot standby mechanism, a double ring network, or the like has been used. This network protocol is reported in, for example, “Resilient Packet Ring” (IEEE802.17, September 2004).
A feature of the RPR protocol conforming to the IEEE802.17 standards resides in effective utilization of a transmission capacity, a high-speed hot standby mechanism, a double ring network, or the like. In the RPR, a so-called called Spatial Reuse Protocol Fairness algorithm has been adopted to realize effective use of a transmission capacity of the RPR ring network.
However, if the transmission capacity of the RPR ring network is increased beyond an upper limit of a physical transmission capacity, in an actual device, it is necessary to replace the original device or card with an RPR device that can use a transmission medium having a larger physical transmission capacity or a card having an RPR function. This causes a problem that a capacity cannot be expanded with an existing device or card.
Further, the RPR protocol defines a system for switching a transmission route in the event of a failure, such as “Wrapping” and “Steering” for a link or node failure. These systems are effective if a failure occurs at one location. However, there arises a problem in that communications between all nodes on a ring cannot be secured if failures occur at plural locations.
As a technique for solving problems of how to expand a transmission capacity and realize a redundant link, there is “Link Aggregation” based on the IEEE802.3ad. This technique is only applicable to a link connecting between two devices. Therefore, there is no way to expand a transmission capacity of an RPR ring or attain redundancy for a network of such a topology that the RPR ring or other such rings include plural nodes. Further, such system is not defined by the IEEE802.17 RPR protocol itself.